Solenoid valve

ABSTRACT

A solenoid valve has a valve closure member ( 5 ) which is positioned in a self-centering manner about a center of rotation (D) between the valve tappet ( 4 ) and the valve seat ( 14 ).

BACKGROUND OF THE INVENTION

The present invention relates to a solenoid valve with a valve housingreceiving a valve closure member that cooperates with a valve tappet anda magnet armature, with the valve closure member being movable to reston a valve seat and the magnet armature being movable to rest on amagnet core, with a valve housing in which the magnet armature isaxially movably guided, and with a magnet coil arranged at the peripheryof the valve housing for the purpose of energizing the magnet armatureto adopt a switch position in which the valve closure member is able toclose the pressure fluid connection between at least one pressure fluidinlet channel and one pressure fluid outlet channel in the valve housingin opposition to the effect of a valve spring.

In a prior art solenoid valve of the type indicated (DE 101 17 608 A1),the valve closure member is designed as a valve piston which must beguided precisely along its peripheral surface in the valve housing. Thisnecessitates close tolerances of fit and an exact alignment of the valveseat in relation to the valve closure member. Further, it issophisticated that the magnet armature must be designed so as to beremovable for inserting the valve seat, the sealing ring and the partsassociated with the sealing ring into the valve housing.

In view of the above, an object of the invention is to provide asolenoid valve which does not suffer from the above-mentioned drawbacks.

SUMMARY OF THE INVENTION

According to the invention, this object is achieved for a solenoid valveof the indicated type by arranging the valve closure member in aself-centering manner around a point of rotation between the valvetappet and the valve seat.

Further features, advantages and possible applications of the inventionbecome apparent from the description of an embodiment.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a cross-sectional view of a solenoid valve configured as atwo-way/two-position seat valve.

DETAILED DESCRIPTION OF THE DRAWING

The solenoid valve includes a valve housing 10 designed in acartridge-type construction and being preferably made ofcorrosion-resistant steel. In terms of manufacturing technique, valvehousing 10 is preferably designed as a turned part in conformity withthe demands of automation and is fastened in a valve block by means of apress fit engagement. In order to realize a uniform pressing force andproper sealing of the valve housing 10 in the valve block, the valvehousing 10 has circumferential flutes 26 at its periphery, grooves, orsaw teeth. In addition, the flutes 26 allow durably depositing the wearparticles being produced in the pressing operation in the flutes 26 sothat contamination of the channels in the valve housing 10 is prevented.The mid-portion of the valve housing 10 is configured as a tubularmagnet core 6, with the result that the magnet core 6 together with thevalve housing 10 forms a one-part assembly. An extremely thin-walledsleeve 2, which is preferably deepdrawn and closed like a bowl in theend section, is seated on the magnet core 6. Sleeve 2 accommodates inits end section a massive end plate 9 and forms the top part for closingthe valve housing 10. End plate 9 dampens the stop noise of the magnetarmature 8, on the one hand, while, on the other hand, the gas containedin the pressure fluid can collect in a chamber of the sleeve 2 formed bythe end stop 9 so that lubrication of the moved magnet armature 8 bymeans of the pressure fluid is constantly ensured. This is because ifthe gas collected in the sliding area of the magnet armature 8, thelubricating film would be interrupted, and undesirable armature wearwould be imminent.

The magnet armature 8 movably arranged below the end plate 9 in thesleeve 2 is connected to a tubular valve tappet 4 introduced into astepped bore 11 of the magnet armature 8. A particularly simple, yetnevertheless reliable connection between the magnet armature 8 and thevalve tappet 4, according to the invention, is achieved in that amandrel introduced from above into the hollow valve tappet 4 is used toradially expand the wall of the valve tappet 4 so that the wall of thevalve tappet 4 is displaced into the transverse flutes 27 of the magnetarmature 8. This attachment can be employed in a favorable manner whenthe material of the valve tappet 4 is softer than the material of themagnet armature 6. In addition, the proposed attachment safeguards asimple, precise adjustment of the residual air slot between the magnetarmature 8 and the magnet core 6 so that the desired constantelectromagnetic properties can be maintained independently ofmanufacturing tolerances.

Arranged between the magnet armature 8 and the end plate 9 in the magnetarmature chamber is a resetting spring 1 which is guided in sections forthe reliable alignment in the stepped bore 11. Succeeding the connectioncomposed of the magnet armature 8 and valve tappet 4 is a piston-shapedvalve closure member 5 which, just as the valve tappet 4, is disposedwithin the centrally positioned through-bore 12 of the valve housing 10.To this end, the through-bore 12 is designed as a stepped bore which, inits bottom expanded stepped portion, accommodates the valve closuremember 5 and, on top thereof, a bushing 7 fastened in the stepped bore.For the purpose of centering the tappet, the bushing 7 is adapted in itsinside diameter either directly to the outside diameter of the valvetappet 4 or, according to the illustrated design, to a bowl 20 securedto the tappet end. Bowl 20 is composed of a material that is hardercompared to the material of the valve tappet or, respectively, amaterial whose surface is hardened. Bowl 20 is press fitted on the endof the valve tappet 4 that faces the valve closure member 5.

Valve tappet 4 is composed of a material with a low density, inparticular light metal (aluminum, magnesium) or plastics. Thislight-weight tappet material permits reducing the moved masses and hasresilient properties which allow properly mastering the impulse forcesand, thus, mechanical stress. Besides, the proposed construction of thevalve components performing a translation movement allows a generouslysized pressure compensating bore 19 ensuring a valve operationindependent of pressure variations.

The use of ceramics, not only for the valve closure member 5 but alsofor the valve seat 14, provides an optimal precondition for an almostwear-free operation of the solenoid valve.

The curved piston portion of the valve closure member 5 is supported onthe bushing 7 in the de-energized valve switching position. To establisha press fit connection with the valve housing 10, the outside diameterof the bushing 7 is adapted to the inside diameter in the expandedportion of the stepped bore 28, to what end the stepped bore 28, whendesired or required, is furnished with flutes, channels, threads, orlike indentations, in order to safeguard the continuity of the press-inforce that has been mentioned hereinabove.

Under the effect of a valve spring 3, the valve closure member 5 restsin the open, electromagnetically non-energized position on the endsurface of the bushing 7 which in the area of contact with the valveclosure member 5, exactly as the bottom of bowl 20, includes recesses 21for the propagation of pressure fluid in the direction of the magnetarmature chamber.

Suitably, the valve spring 3 is biased by means of a spring stop 13 thatis inserted from below into the opening of the valve housing 10 and isadjustable by means of a thread also within a valve seat stop 22. Thevalve seat stop 22 designed as a massive perforated disc has at itsperiphery an outside thread being in engagement with an inside thread atthe bottom end of the valve housing 10 so that the valve seat stop 22 isscrewed from below into the valve housing 10 until it contacts theannular-disc shaped valve seat 14. It is thus ensured that the valveseat 14 pressured from below into the valve housing 10, under the effectof the high hydraulic pressure, cannot detach itself from its adjustedpress fit engagement with the valve housing 10. In the type of asetscrew, the tubular spring stop 13 is positioned centrally in acentrally disposed threaded bore of the valve seat stop 22.

The biasing force of the valve spring can be adjusted precisely uponelectromagnetic energization in the valve's closing position by turningthe spring stop 13 in the valve seat stop 22. For the precise guiding,the helical valve spring 3 is received with its one end within thetubular valve closure member 5, while the other end of the valve spring3 is supported on a collar of the spring stop 13. The tubular form ofthe valve closure member 5 stepped in its inside diameter thus allows asafe, compact accommodation and support of individual spring coils ofthe valve spring 3 without inhibiting the hydraulic pressurecompensation in the valve housing 10.

At the level of the valve closure member 5 and, hence, above the valveseat 14, the valve housing 10 is horizontally penetrated by a pressurefluid inlet channel 15 which, in the open valve switching position asshown in the drawing, is connected via the open valve seat 14, thepunched valve seat stop 22 and the through-bore in the spring stop 13 tothe pressure fluid outlet channel 16 that opens from below verticallyinto the valve housing 10.

The solenoid valve is hydraulically pressure-balanced, to what end aconcentric, spring-loaded back ring 17 is arranged at the outsideperiphery of the valve closure member 5, said back ring being pressed bya spring 23 supported on the valve seat 14 from below, through a springplate 25 and a sealing ring 24, against a conical portion of the steppedbore 28. With its spherical outside shoulder, the back ring 17 issupported on the conical inside wall of the stepped valve housing 10,with the result that the valve closure member 5 guided within thesealing and back ring 24, 17, similar like in a ball cup, can tiltablymove to all sides in the valve housing 10 to a limited extent. In orderthat also the sealing ring 24 is able to follow a tolerance-inducedinclined position of the spring 34 in a low-resistance manner, thesealing ring is likewise shaped spherically in the direction of thefunnel-shaped spring plate 25. The spherical surfaces of the back ring17 and the sealing ring 24 are the surfaces remote from each other,while the surfaces of back ring and sealing ring 17, 24 that abut oneach other are plane surfaces. Spring 23 ensures both an axial and aradial action of force at the sealing ring 24 in order to safeguard thesealing effect of the sealing ring 24 even at low hydraulic pressures.The mentioned radial preloading force is further needed in order tocompensate the radial thermal expansions of the valve components. Withincreasing hydraulic pressure in the pressure fluid inlet channel 15,advantageously, self-boosting of the sealing effect of the sealing ring24 is achieved. The sealing ring 24 is made of plastics, while the backring 17 is configured as a metal ring. Due to the described design, backring 17 in addition fulfills favorably a static sealing function at theconical inside sealing surface of the valve housing 10.

In order that a sufficient freedom of motion is ensured likewise in thecontact area between the valve closure member 5, the bushing 7, and thebowl 20 for tilting the valve closure member 5, the contact surfacesdisposed between the bushing 7, the bowl 20 and the valve closure member5 also have a spherical contour that is preferably shaped as a sphericalsegment.

The point of rotation D for tilting the piston-shaped valve closuremember 5 is thus disposed on the axis of symmetry of the solenoid valveroughly at half the level of the valve closure member 5. The describedarticulated support and sealing of the valve closure member 5 in thevalve housing 10 will thus safeguard a simple and precise self-centeringof the valve closure member 5 at the funnel-shaped sealing seat of thevalve seat 14. The funnel angle of the valve seat 14 is adapted to thespherical sealing surface of the valve closure member 5, that ispreferably shaped as a spherical segment, and the funnel angle at thevalve seat 14 is chosen to be such that in the case of wear of thesealing edge of the valve seat 14, the mean sealing diameter remains asunchanged as possible in order to thus maintain the exact hydraulicpressure compensation of the solenoid valve without changes even duringlong-term operation.

To reduce the hydraulic resistance, the magnet armature 8, the valvetappet 4, and the valve closure member 5 are penetrated by severalpressure compensating bores 19 in parallel to the valve's axis ofsymmetry. The pressure fluid flowing into the pressure fluid outletchannel or pressure fluid inlet channel 16, 15 is thus not hindered topropagate through the pressure compensating bore 19 that penetrates thevalve closure member 5, the valve tappet 4 and the magnet armature 8,into the magnet armature chamber and, hence, to the end section of thesleeve 2 so that an almost constant switching characteristics of thesolenoid valve is favorably ensured irrespective of pressure andtemperature differences of the fluid.

The following description briefly illustrates the mode of operation ofthe solenoid valve with the features essential for the invention. In theillustration according to FIG. 1, the solenoid valve adopts theelectromagnetically non-energized, open basic position in which anunhindered pressure fluid connection between the pressure fluid inletchannel 15 and the pressure fluid outlet channel 16 is ensured due tothe valve closure member 5 that has lifted from the valve seat 14. Inthis basic position, the end surface of the valve closure member 5remote from the valve seat 14, under the effect of the valve spring 3,rests on the end surface of the bushing 7. Bushing 7 is arranged in thethrough-bore 12 of the magnet core 6 in such a fashion that in the openvalve position, the magnet armature 8 attached to the valve tappet 4 isremote from the magnet core 6 by at least a rate corresponding to thevalve stroke. In the open valve position, the end surface of the magnetarmature 8 remote from the magnet core 6 is hence equally spaced adefined axial distance from the end plate 9 at the dome-shaped portionof the sleeve 2, whereby a so-called damping stroke of the magnetarmature 8 is rendered possible to be able to slow down the magnetarmature 8 according to the following description of functioning afterthe demagnetization.

Initially, however, when the electromagnetic energization of the valveoccurs, the valve closure member 5 moves away from the bushing 7 in adownward direction and, due its tiltability, in a self-centering mannercomes into abutment on the valve seat 14. During this operation, theresetting spring 1 will automatically be relieved and, compared thereto,the valve spring 3 is preloaded in proportion to the valve stroke untilthe magnetic field of the magnet coil 18 collapses after deactivation ofthe electromagnetic energization (demagnetization). Thereafter, thevalve spring 3 which is stiffer compared to the resetting spring 1becomes effective in the sense of valve opening, accelerating the valveclosure member 5, the bowl 20, the valve tappet 4 and the magnetarmature 8 in opposition to the effect of the initially weak resettingspring 1 in the direction of the end plate 9. This acceleration of thetotal mass comprising the valve closure member 5, the bowl 20, the valvetappet 4, and the magnet armature 8 advantageously takes place onlyuntil the valve closure member 5 has moved into abutment on the bushing7 so that the force of the valve spring 3 which was originally active onthe valve tappet 4, the bowl 20 and the magnet armature 8 will only acton the valve closure member 5 that came to rest on the bushing 7.Consequently, it will only be the mass of magnet armature, bowl andvalve tappet, reduced by the mass of the valve closure member 5, thatwill continue to move due its mass inertia in opposition to thestroke-proportionally rising force of the resetting spring 1 in thedirection of the end plate 9. With increasing compression of theresetting spring 1 and in consideration of the viscous damping of thepressure fluid disposed in the magnet armature chamber, the magnetarmature 8 and the valve tappet 5 are decelerated during the dampingstroke until standstill shortly before the end plate 9 or underextremely unfavorable conditions (dry operation, frothed fluid) directlyon the end plate 9, with a subsequent reversal of the direction ofmotion of the magnet armature 8 and valve tappet 4, initiated by theresetting spring 1, into the rest position according to the drawing,where the valve tappet 4 abuts on the valve closure member 5 again. Asthis occurs, it must be taken into consideration that the impulse forceacting in the direction of the end plate 9 and, after the reversal ofmovement, in the direction of the valve closure member 5 as well as thenoise of impact will be reduced considerably due to the resilientproperties of the valve tappet 4.

LIST OF REFERENCE NUMERALS

-   1 resetting spring-   2 sleeve-   3 valve spring-   4 valve tappet-   5 valve closure member-   6 magnet core-   7 bushing-   8 magnet armature-   9 end plate-   10 valve housing-   11 stepped bore-   12 through-bore-   13 spring stop-   14 valve seat-   15 pressure fluid inlet channel-   16 pressure fluid outlet channel-   17 back ring-   18 magnet coil-   19 pressure compensating bore-   20 bowl-   21 recess-   22 valve seat stop-   23 spring-   24 sealing ring-   25 spring plate-   26 flute-   27 transverse flute-   28 stepped bore

1. A solenoid valve, with a pressure fluid Inlet channel and a pressure fluid outlet channel within a valve housing receiving a valve closure member that cooperates with a valve tappet and a magnet armature to control a pressure fluid connection between the inlet channel and the outlet channel, with the valve closure member being movable to rest on a valve seat and the magnet armature being movable to rest on a magnet core and being axially movably guided within the valve housing, with a valve spring biasing the valve member away from the valve seat, and with a magnet coil arranged at the periphery of the valve housing for the purpose of energizing the magnet armature to adopt a switch position in which the valve closure member is able to close the pressure fluid connection In the valve housing in opposition to the effect of the valve spring, wherein valve closure member (5) is arranged in a self-centering manner around a point of rotation (D) between the valve tappet (4) and the valve seat (14), wherein the valve closure member (5) has a tubular design, and the point of rotation (D) is positioned within the valve closure member (5) on the axis of rotational symmetry of its body, and wherein the valve closure member (5) includes at its outside periphery a back ring (17) which swivels about the point of rotation (D) synchronously with a self-centering tilting movement of the valve closure member (5) and seals the valve closure member (5) along its periphery in the valve housing (10).
 2. The solenoid valve as claimed in claim 1, wherein the back ring (17) includes an outside shoulder shaped as a section of a sphere defined by its radius around the point of rotation (D) and wherein the valve housing (10) comprises a conical inside wall abutted by the shoulder.
 3. The solenoid valve as claimed in claim 2, wherein between the back ring (17) and the conical inside wall of a spring plate (25), a sealing ring (24) is axially and radially preloaded by means of a spring (23) that is supported on the valve seat (14). 